ISPConfig e-mail problems

I have a new install of ispc on Ubuntu and all works well except for receiving mail. I have configured outlook express and read up loads on here and the net but still scratching my head.
I can send/receive ok in oe with no errors and send mail ok but cannot receive mail.

Most likely the receiving SMTP server runs some sort of RBL checks and perhaps another on known dialup lines. If so, even unlisting your ip wouldn't change much, as your IP can be traced down to be a dialup one and will sometimes be blocked.
I don't think you will be able to "unlist" the ip as you'll get another one after a reconnect with your ISP and the play starts again.

I already pay a company to host my sites for me and I wanted to get away and host myself, but my current isp is obviously the problem, so I have shifted everything back to the hosting company for now as in 2 weeks I will obtain my mac code and move to a better isp with a static ip service that does not block port 25 and then shift everything back to my linux box here.

I have now switched to an isp with static ip and all is ok on that side.

But now I can send mails ok using outlook express, but get

Code:

This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:
[email protected]
No Such User Here

If I send a mail from a web based e-mail, google, the mail delivers ok and drops into my inbox on outlook express, but if I use another mail account which is on the server I am currently renting then it gets sent back with the error.